Ignition coil system



June 1, 1937- F. D. BENTLEY IGNITION COIL SYSTEM Filed Aug. 28, 1954 INVEN T016 PLUGS m w 1 V 3 W E a m n em D m a J a z 6 5 n, 0 ml 1W WM, 5 AM F m g y i v N 0 5 M n 1 o 1 1 r 6 m 5 i M 6 1 1 l: 5 M 5 7 5 III: J F1 n n /8 m 1 M 3 9 4 a f a F l 1 1 5 v T 6/ M Patented June 1, 1 937 IUNITED STATES PATENT OFFICE IGNITION COIL SYSTEM Delaware ApplicationAugust 28, 1934, Serial No. 741,763

12 Claims. (Cl. 175-361) This invention relates to ignition coils forgasoline motors and the like, and has particular reference to a devicefor the elimination of static interference when radio apparatus isemployed in the immediate vicinity of an internal combustion engine.

Various devices have been resorted to in the past for suppression of theinterference above referred to. Among these are the so-called supmpressors" which are applied to the spark plugs. Various forms ofelectrostatic shielding have. also been provided for isolating a radioreceiver from static effects of an ignition system. Since the radioapparatus is usually operated from the 15 some battery as that whichserves the ignition system, shielding does not provide the completeisolation of the radio receiver which is desired. l have discovered,however, that the structure of the ignition coil may be so designed asto very 2Q considerably reduce the interference both as transmittedthrough space between the ignition system and the radio receiver, andalso as transmitted through the conductors to the common battery.

25 it is an object of my invention to provide an ignition system theelectrical characteristics of which are such as to substantiallyeliminate sparking interference with the ordinary operation oi a radioreceiver.

3@ Other objects of my invention are: to provide an ignition coilstructure suitable ffor u'se in an ignition system whose battery iscommon to that oi a radio receiver; to provide adequate shielding in anignition coil such that static interference, 35 at above referred to, issubstantially suppressed; and to provide means for substantiallyeliminating a so-called corona-effect which, if it takes place betweenthe primary and secondary windings of an ignitioncoil, is a contributingcause of 40 static interference.

The foregoing and other objects of my inven tion will beapparent uponreading a complete description thereof, details of which are given inthe ensuing part of the specification wherein ref- 45 erencfe is made tothe accompanying drawing in core 3 about which is wrapped a sheet ofinsulating material 4. The secondary winding 5 is preferably disposednext to the insulation 4 and internally of primary winding 6. Betweenthe primary and secondary windings, Iprovide an elec- 5 trostatic shieldl, faced on both sides thereof by insulating members 8 and 9. The shieldI may be composed of sheet copper. The usual precautionsare taken thatthe abutting edges of the shield 5 do not make contact with one another,10 since, it they did, an undesirable sho-rt-circuited loop would beprovided for induced currents therein.

The arrangement of the coil leads contributes most effectively to theefficiency of operation of my invention. Preferably, the starting leadof the secondary winding is connected to a sheet metal member iii which.is disposed about one end of the laminated core 3. A molded insulationend piece it is so constituted as to provide on the inner side a cupinto which the laminated core 3 may fit. The sheet metal member illintervenes between the Aamlnations oi the core and the inner wall ofthis cup. The molded member l l is also provided with an outer cup whichmay, if desired, be lined by a metallic receptacle it. After theignition coil unit has been assembled, a mall 83, or the like, may bedriven through a central hole in the insulation member I l therebyelectrically interconnecting the cup lining it, the

sheet metal lead Hi, which connects with the starting lead ofthesecondary winding 5 and the laminations of the core 3.

The finish lead of the secondary winding and the start lead of theprimary winding are connected by a conductor l4 (common to both) to aterminal post l5 so that connection may be made with the breaker-pointsl6 (see Fig. 2) of' the ignition system.

The outer lead of the primary winding may be 40 connected as by means ofa conductor I!- to a terminal post It fol-connection with an ignitionswitch l9. Another end piece 20 of molded insulation is provided with aninternal cup for holding the core in position.- The molded end pieces IIand 20 may; therefore, be seen to be similar in construction except thatthe member ll only is provided with areceptacle for an ignition wire tothe distributor 29.

The assembly of my ignition coil unit may be I 1 completed by encasingthe unit within the outer cylindrical member 2|, the ends of which maybe permanently locked into engagement with metal flanges 22. The letter,if desired, may be molded illtothe peripheries or the members II and 20respectively. The edges of the members 22 may be spun over the flangedportions of the casing member 2i. The'entire ignition coil unit may, ifdesired, be supported by a 'clamp 23, or in any other desired manner.

In order to prevent induced currents in the members 2i and 22, theseparts are split and the intervening space is preferably filled withinsulating compound. The clamp 23, if it is in two pieces, may beprovided with insulation members ll about the bolt 32 so as to avoid ashort circuit for induced currents.

The electrostatic shield I may be electrically connected to the outershell II as by means of a conductor 33. These elements may then begrounded in any suitable manner; for example, through the clamp members23 which, presumably are supported by a metallic portion oi the chassis.

It will be noted that the cylindrical walls of the insulation member ilextend considerably beyond the ends of the coils. The purpose of thisarrangement is to avoid a corona effect which has been known to takeplace between the primary and secondary coils. This effect is veryobjectionable.

. The very marked improvement in the operating characteristics in myignition coil unit, as compared with units heretofore known, may beattributed in part to the arrangement of the coil leads I adiacent theelectrostatic shield i. These particular coil leads are at the lowpotential ends of the primary and secondary respectively.

Referring to Fig. 2, I show the relation between the connections to myignition coil unit and the other elements of my ignition system such ascontribute further to the improved performance characteristics of thesystem as a whole. In this diagram will be seen the common battery llgrounded at one end and having a lead at the other end to the ignitionswitch i 9. The ignition switch is preferably shunted by a capacitor 25having a value of the order of say .5 mi. The ignition switch is, asbefore stated, connects with the terminal post l8 of the ignition coilunit. A conductor 20 is shown interconnecting the breaker points it withone lead each of the primary and secondary windings, the leads beingconnected to the terminal post I! (Fig. 1). The

-breaker points may, if desired, be shunted by a capacitor 21 havingpreferably a value of about .25 mt.

A conductor 20 interconnects the-terminal ll ing a core member, primaryand secondary windings, an electrostatic shield separating the primaryfrom the secondary, insulating means disposed internally and externally01' said shield. a

terminal post common to the outer lead of the inner winding and to theinner lead of the outer winding, a grounded metallic outer casing, andmeans including an electrical connection between said shield and saidcasing for substantially suppressing the eifects of ignition-circuitinterference upon a nearby radio apparatus.

2. An ignition circuit transformer comprising a core, an insulatingmember surrounding said core, a secondary winding about said insulatingmember, an inner and an outer insulating sleeve surrounding saidsecondary winding, a grounded electrostatic shield disposed between saidinner and outer sleeves, a primary winding exterior. to said outersleeve, a grounded metallic casing for said transformer, a binding postfor the outer lead of said primary winding, a distributor leadreoeptacle connected both to said core and to the inner lead of saidsecondary winding, and means including a conductor common to the innerlead of said primary winding and the outer lead of said secondarywinding for substantially preventing the radiation of ignition-circuitinterference to a zone occupied by radio apparatus.

3. An ignition circuit transformer comprising shieldingly encasedprimary and secondary coils. a grounded electrostatic shield of thinmetal interposed between said primary and said secondary, abreaker-point connection'to the outer terminal of said secondary and theinner terminal of said primary, an ignition switch connection to theouter terminal of said primary, a laminated iron core, and meansincluding a distributor connection to the inner terminal of saidsecondary and to said core for substantially suppressing the eifects oiignition-circuit interference upon a nearby radio apparatus.

4. An ignition circuit transformer in accordance with claim 3 and havingmeans including laminations of insulating material between which saidelectrostatic shield is disposed, at least one of said laminationsextending substantially beyond the lengthwise limits of the coilconvolutions.

5. In a transformer, a secondary coil, a primary coil wound over saidsecondary, ignitioninterference shielding means insulatingly interposedbetween said primary and said secondary, a conductor interconnecting theflnish-lead of said secondary and the "-lead of said primary, separateconductors to the start"-lead 'of said secondary and to thefflnish leadof said primary, respectively, an outer metallic casing and a groundedconnection both to said casing and to said shielding means.

6. In a device for suppressing the interference effect upon radioapparatus caused by an ignition system, an ignition transformer havingprimary and secondary coils, a split tubular casing therefor of magneticmaterial which is grounded, a grounded electrostatic shield separatingsaid primary from said secondary, and means including a tubular memberof insulating material' over-reaching the coil ends and the shield endssumciently to substantially eliminate corona leakage between said coilsand from either of said coils to said shield.

7. An ignition-circuit transformer for internal combustion enginescomprising in combination .core member, primary and secondary windings,

an electrostatic shield separating nil from said secondary, a containerfor said windings having a split cylindrical wall of magnetic materialand end pieces of non-metallic material, and means includingra groimdedconductor connecting with said shield and with the cylindrical wall ofsaid container for substantially suppressing the effects ofignition-dreuit interference upon a nearby radio apparatus.

8. A transformer for use with a bat- 2 7 system for a radio apparatusand'for the ignition circuit of an internal combustion engine,comprising primary and secondary windings, a core member electricallyconnected tothe' 7s start"-lead of the inner one of the two saidwindings, a metallic ignition-interference shield separating saidwindings, a metallic container surrounding said windings, a groundterminal for said shield and said container, and a breaker; point commonto the finish"-lead of the inner winding and to the start-lead of theouter winding.

9. The invention as set forth in claim 8 wherein means including aninsulation member are provided adjacent said ignition -interferenceshield for substantially suppressing a corona discharge loetween saidwindings and from either of said windings to said shield.

10. in a transformer, primary and secondary coils wound one over theother, ignition-interierence shielding means insulatingly interposedbetween said coils, a laminated core and a cylindrical container both ofmagnetic material, means including a conductor common to said shieldingmeans and to said cylindrical container 101' maintaining the same atsubstantially ground potential. means i'or equalizing potentials appliedto the finish-lead ofthe inner coil and to the start"-lead of the outercoil, and means for equalizing potentials applied to the "start"- leadof the inner coil and to the laminated core.

11. A device in accordance with claim 10 characterized in that saidignition-interference shielding means and said cylindrical container areso constructed as to offer substantially an infinite impedance toinduced currents circulating therein,

12. In a device for suppressing the interference efiect upon radioapparatus caused by the ignition system of an internal combustionengine, a transformer having primary and secondary windings, anelectrostatic shield separating said windings, and means includingmembers of insulating material at least one of which over-reaches theedges of said shield sufficiently to substantial lyeliminate coronaleakage between said windings and said shield.

FERDON' D. BENTLEY.

